Adverb-modified verbs called with brackets.

```
+/:[2;1 2 3]
``` 
was NYI error, this merge makes it work, I believe.

This is important if one considers higher order functions, e.g.:

```
  flip:{[f;x;y]f[y;x]};       / call a dyadic verb with its arguments flipped
  flip[-][2;3]                    / this is OK
1
  flip[-\:][2;1 2 3]            / and this is not, because it gets transformed to -\:[1 2 3;1]
nyi error                    

       
  flip[-\:][2;1 2 3]            / but it's OK in my version as well as in K2.8
-1 0 1                         
```